JPH08201741A - Optical waveguide type optical modulator - Google Patents

Abstract

PURPOSE: To obtain intensity-modulated light with the value of a low voltage for modulation at a high speed with the optical waveguide type optical modulator which is formed with an optical waveguide having compd. semiconductor multiple quantum well layers on a compd. semiconductor substrate and in which the well layers of the compd. semiconductor multiple quantum well layers consist of a quaternary system of InGaAlAs and the barrier layers of the compd. semiconductor multiple quantum well layers consist of a ternary system of InAlAs. CONSTITUTION: The well layers 3a of the compd. semiconductor multiple quantum well layers 3 have a thickness of <=20nm thicker than 12nm and the quaternary system of the InGaAlAs constituting the compd. semiconductor multiple quantum well layers 3 have the compsn. with which the wavelength apart by 25 to 38meV in view of the value in terms of energy of the wavelength from the wavelength of the incident light on the optical waveguide 5 in a direction shorter than this wavelength is obtainable as the absorption end wavelength of the compd. semiconductor multiple quantum well layers 3. The compd. semiconductor barrier layers 3b have a thickness of <5nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide type optical modulator.

[0002]

2. Description of the Related Art Conventionally, an optical waveguide type optical modulator described below with reference to FIG. 7 has been proposed.

That is, (i) and (a) are formed on a compound semiconductor substrate 1 made of InP having n-type as a first conductivity type.
A compound semiconductor clad layer 2 made of InAlAs ternary having n-type as the first conductivity type, and (b) a compound semiconductor quantum well layer 3a and a compound semiconductor barrier layer 3b are sequentially laminated alternately. And a compound semiconductor in which neither an impurity imparting n-type as the first conductivity type nor an impurity imparting p-type opposite to the n-type as the first conductivity type as the second conductivity type is intentionally introduced. The multi-quantum well layer 3 and (c) the compound semiconductor clad layer 4 of InAlAs ternary system having p-type as the second conductivity type are laminated in that order, and (ii) modulated. The light incident end surface 5a on which the light L to be incident is incident and the light L to be modulated
The optical waveguide 5 having the light emitting end face 5b from which the intensity-modulated light L'is emitted.

In this case, the compound semiconductor multiple quantum well layer 3
The compound semiconductor quantum well layer 3a forming the
The thickness L _{a is} 12 nm or less (for example, 8 nm), which is _a quaternary system of aAlAs and thinner than the Bohr radius.
And the quaternary system of InGaAlAs that composes the compound semiconductor quantum well layer 3a is In _1-xy G
a _x Al _y when expressed by the chemical formula of As, the x in the formula for example 0.435, the composition to a value of y for example 0.035, thus, for example, In _0.53 Ga _0.435 Al _{0.03 5} As
It has a composition represented by.

Further, the compound semiconductor barrier layer 3b constituting the compound semiconductor multiple quantum well layer 3 is a ternary system of InAlAs and the wave function is the compound semiconductor barrier layer 3 concerned.
A thickness L _{b of} 5 nm or more, which is obtained with almost no overlap with the compound semiconductor quantum well layer 3a adjacent to b, but not more than the thickness of the compound semiconductor quantum well layer 3a (for example,
InA having the same thickness as the compound semiconductor quantum well layer 3a) and constituting the compound semiconductor barrier layer 3b.
When the ternary system of 1As is represented by the chemical formula of In _1-Y Al _Y As, it has a composition in which y in the chemical formula is, for example, 0.47, and thus is represented by In _0.53 Al _0.47 As, for example. .

Further, a first electrode 7 is provided on the optical waveguide 5 via a compound semiconductor electrode attachment layer 6 made of an InGaAs ternary system having a p-type as a second conductivity type.

Further, the optical waveguide 5 of the compound semiconductor substrate 1
The second electrode 8 is attached to the side opposite to the side.

The above is the configuration of the conventionally proposed optical waveguide type optical modulator.

According to the conventional optical waveguide type optical modulator having such a configuration, when the light L to be modulated is made to enter the optical waveguide 5 from the light incident end face 5a side, the light L is generated. The modulation voltage V _i propagates inside the optical waveguide 5 toward the light emitting end face 5b, and at this time, the first electrode 7 side is negative between the first electrode 7 and the second electrode 8. Is applied, the absorption of excitons in the compound semiconductor multiple quantum well layer 3 forming the optical waveguide 5 is controlled in accordance with the value of the modulation voltage V _i , thereby propagating in the optical waveguide 5. Is obtained by being modulated into the light L ′ whose intensity is modulated according to the value of the modulation voltage V _i , and the light L ′ whose intensity is modulated is emitted from the light emitting end face 5b and is obtained outside. The function as an optical waveguide type optical modulator can be obtained.

In this case, in the optical waveguide 5, the compound semiconductor multiple quantum well layer 3 in which the compound semiconductor quantum well layers 3a and the compound semiconductor barrier layers 3b are alternately laminated in sequence.
The intensity-modulated light L ′ is composed of
And to obtain the same degree of modulation as the case where the optical waveguide 5 was made of a compound semiconductor layer composed of the same compound semiconductor and the compound semiconductor quantum well layer 3a instead of compound semiconductor multiple quantum well layer 3, the modulation voltage V _i In comparison with the case where the optical waveguide 5 is made of a compound semiconductor layer made of the same compound semiconductor as the compound semiconductor quantum well layer 3a instead of the compound semiconductor multiple quantum well layer 3, it can be obtained at a low value, and The light L to be modulated is converted by the modulation voltage V _i by
The optical waveguide 5 can be modulated at a higher speed than in the case where the optical waveguide 5 is made of a compound semiconductor layer made of the same compound semiconductor as the compound semiconductor quantum well layer 3a instead of the compound semiconductor multiple quantum well layer 3.

The compound semiconductor quantum well layer 3a forming the compound semiconductor multiple quantum well layer 3 is InGaA.
Since it is composed of a quaternary system of 1 As, the compound semiconductor quantum well layer 3
InGa instead of InGaAlAs quaternary system
Even if it has a thicker thickness than in the case of using the ternary system of As, the absorption edge wavelength of the compound semiconductor multiple quantum well layer 3 is calculated from the wavelength λ ₀ (for example, 1.55 μm) of the light L to be modulated. Since the intensity L-modulated light L ′ can be set within a short wavelength range, the compound semiconductor quantum well layer 3a is replaced with InG instead of the InGaAlAs quaternary system.
It can be obtained with high efficiency as compared with the case of using the ternary system of aAs.

Further, the compound semiconductor barrier layer 3b forming the compound semiconductor multiple quantum well layer 3 is made of InAlAs.
Of the compound semiconductor barrier layer 3b,
The barrier height between the compound semiconductor quantum well layer 3b and the compound semiconductor quantum well layer 3b can be set small for holes but large for electrons. Therefore, the light L to be modulated has high intensity. However, due to the accumulation of holes in the interface between the compound semiconductor quantum well layer 3a and the compound semiconductor barrier layer 3b, the light L to be modulated is saturated by the modulation voltage V _i or the operation is saturated. The light L to be emitted is the modulation voltage V
There is no reduction in the speed of the operation modulated by _i .

[0013]

However, in the case of the conventional optical waveguide type optical modulator, the compound semiconductor quantum well layer 3a forming the compound semiconductor multiple quantum well layer 3 is thinner than the Bohr radius but is 12 nm. Since it has only the following thickness L _a, the absorption of excitons in the compound semiconductor multiple quantum well layer 3 is, as shown in FIG.
Is a TE wave, there are two types of absorption: absorption of excitons composed of heavy holes and heavy electrons and absorption of excitons composed of light holes and light electrons at a wavelength position distant from the absorption wavelength position. When the light L to be modulated is a TM wave, it consists only of absorption of excitons consisting of light holes and light electrons, and moreover, the compound semiconductor multiple quantum well layer 3 included in the optical waveguide 5. The absorption edge wavelength of the compound semiconductor multiquantum well layer 3 is shifted by the modulation voltage V _i applied between the first and second electrodes 7 and 8 The thickness of the semiconductor quantum well layer 3a is generally L, and the first and second electrodes 7 and 8 are
When the intensity of the electric field applied to the compound semiconductor multiple quantum well layer 3 by the modulation voltage V _i applied in between is generally F, it is proportional to (L ⁴ · F ² ), and is called the quantum confinement Stark effect. ), The shift amount ΔE
However, as shown in FIG. 9, only a relatively small value is obtained, and accordingly, the absorption coefficient of the compound semiconductor multiple quantum well layer 3 is TE wave as the light L to be modulated. 10 and the TM wave have different values and can be obtained only with a relatively small value. Therefore, the intensity-modulated light L ′ is converted into the modulation voltage V as shown in FIG. _It has a drawback that it cannot be obtained at a high speed with a low value such as less than 2V of _i .

Further, the compound semiconductor barrier layer 3b constituting the compound semiconductor multiple quantum well layer 3 has a thickness of 5 nm or more but not more than the thickness of the compound semiconductor quantum well layer 3a, and However, since the compound semiconductor barrier layer 3b does not contribute to the change of the absorption coefficient of the compound semiconductor multiple quantum well layer 3, the intensity-modulated light L '
However, it has a drawback that it cannot be obtained at a high speed with a low value of the modulation voltage V _i .

Therefore, the present invention does not have the above-mentioned drawbacks.
We propose a new optical waveguide type optical modulator.

[0016]

The optical waveguide type optical modulator according to the present invention is (a) a compound having the first conductivity type as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. A structure in which (i) (a) a compound semiconductor clad layer having a first conductivity type, (b) a compound semiconductor quantum well layer, and a compound semiconductor barrier layer are sequentially and alternately laminated on a semiconductor substrate, and A compound semiconductor multiple quantum well layer in which neither an impurity giving a first conductivity type nor an impurity giving a second conductivity type opposite to the first conductivity type is intentionally introduced, and (c) a second conductivity And a compound semiconductor clad layer having a mold are laminated in that order, and (ii)
An optical waveguide having a light incident end surface on which the light to be modulated is incident and a light emitting end surface from which the intensity-modulated light of the light to be modulated is emitted is formed, and (b) on the optical waveguide, The first electrode is attached via the compound semiconductor electrode attachment layer having the second conductivity type, and (c) the compound semiconductor quantum well layer forming the compound semiconductor multiple quantum well layer is made of InGaAlAs. The quaternary system has a thickness smaller than the Bohr radius, and (d) the compound semiconductor barrier layer forming the compound semiconductor multiple quantum well layer is a ternary system of InAlAs and has a wave function. Has a thickness obtained with almost no overlap with the compound semiconductor quantum well layer adjacent to the compound semiconductor barrier layer.

However, the optical waveguide type optical modulator according to the present invention is the optical waveguide type optical modulator having the above-mentioned structure. (E) The compound semiconductor quantum well layer constituting the compound semiconductor multiple quantum well layer. Is thicker than 12 nm but not more than 20 nm, and (f) the InGaAlAs quaternary system constituting the compound semiconductor quantum well layer of the compound semiconductor multiple quantum well layer is the optical waveguide described above. A wavelength separated by 25 to 38 meV from the wavelength of the light to be modulated entering the light incident end face in the direction shorter than the wavelength is obtained as the absorption edge wavelength of the compound semiconductor multiple quantum well layer. In addition, (g) the compound semiconductor barrier layer forming the compound semiconductor multiple quantum well layer has a thickness of less than 5 nm.

[0018]

According to the optical waveguide type optical modulator of the present invention, the compound semiconductor quantum well layer forming the compound semiconductor multiple quantum well layer has a thickness of more than 12 nm but 20 nm or less, InGaAlA forming the compound semiconductor quantum well layer of the compound semiconductor multiple quantum well layer
The wavelength at which the quaternary system of s is 25 to 38 meV away from the wavelength of the light to be modulated which is incident on the light incident end face of the optical waveguide in the direction shorter than the wavelength as the absorption end wavelength The conventional optical waveguide structure described above with reference to FIG. 7 except that it has the composition obtained and that the compound semiconductor barrier layer forming the compound semiconductor multiple quantum well layer has a thickness of 5 nm or less. Since the optical modulator has the same configuration as that of the optical modulator, detailed description thereof will be omitted.
As in the case of the conventional optical waveguide type optical modulator described above,
If the light to be modulated is made incident from the light incident end face side into the optical waveguide, and at this time, a modulation voltage is applied between the first electrode 7 and the second electrode, the light is modulated. Similar to the case of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, that the light whose intensity is modulated according to the value of the modulation voltage is emitted to the outside from the light emitting end face, A function as an optical waveguide type optical modulator can be obtained.

Further, as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, the optical waveguide is a compound semiconductor multiple layer in which compound semiconductor quantum well layers and compound semiconductor barrier layers are alternately laminated. Since the quantum well layer is used, a detailed description thereof will be omitted, but the intensity-modulated light L ′ is omitted.
As compared with the case of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, in comparison with the case where the optical waveguide is made of a compound semiconductor layer made of the same compound semiconductor instead of the compound semiconductor multiple quantum well layer, It can be modulated at high speed.

Further, the compound semiconductor quantum well layer forming the compound semiconductor multiple quantum well layer is made of InGaA as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG.
Since it is a quaternary system of 1As, detailed description thereof will be omitted. However, the intensity-modulated light is converted into In by the compound semiconductor quantum well layer as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG.
Instead of GaAlAs ternary system, InGaAs 3
It can be obtained with higher efficiency than in the case of the original system.

Further, since the compound semiconductor barrier layer constituting the compound semiconductor multiple quantum well layer is made of InAlAs ternary system as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. Although detailed description is omitted, as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, even if the light to be modulated has a high intensity, the light to be modulated has a voltage for modulation. Saturation does not occur in the operation modulated by, and the speed of the operation in which the light to be modulated is modulated by the modulation voltage does not decrease.

However, in the case of the optical waveguide type optical modulator according to the present invention, the number of compound semiconductor quantum well layers constituting the compound semiconductor multiple quantum well layer included in the optical waveguide is 12
thicker than 20 nm but less than 20 nm, and
The thickness thereof is thicker than that of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, and the quaternary system of InGaAlAs forming the compound semiconductor quantum well layer is formed on the light incident end face of the optical waveguide. From the wavelength of the incident light to be modulated, the energy conversion value of the wavelength in the direction shorter than that wavelength is 25-
Since the wavelengths separated by 38 meV have a composition that can be obtained as the absorption edge wavelength of the compound semiconductor multiple quantum well layer, the absorption of excitons in the compound semiconductor multiple quantum well layer can be suppressed even when the light to be modulated is a TE wave. Even in the case of TM wave, the absorption of excitons composed of heavy holes and heavy electrons and the absorption of excitons composed of light holes and light electrons are mixed absorptions at wavelength positions of almost the same absorption. Moreover, the absorption edge wavelength of the compound semiconductor multiple quantum well layer included in the optical waveguide is shifted by the modulation voltage applied between the first and second electrodes, and the shift amount is the TE wave of the light to be modulated. 7 and the TM wave, a significantly larger value can be obtained as compared with the case of the conventional optical waveguide type optical modulator described above with reference to FIG. The absorption coefficient of the quantum well layer has almost the same value regardless of whether the light to be modulated is a TE wave or a TM wave, and the conventional optical waveguide type optical modulator described above with reference to FIG. In this case, the intensity-modulated light is obtained with a much larger value than that of the conventional optical waveguide type optical modulator described above with reference to FIG. In comparison with the case of the conventional optical waveguide type optical modulator described in 7 above, a low value can be obtained at high speed.

Further, the compound semiconductor barrier layer constituting the compound semiconductor multiple quantum well layer has a thickness of less than 5 nm, and the thickness of the compound semiconductor barrier layer is the conventional optical waveguide type optical modulation described above with reference to FIG. Since it is thinner than the case of the optical modulator, the intensity-modulated light can be obtained at a high speed with a value of the modulation voltage lower than that of the conventional optical waveguide type optical modulator described in FIG.

[0024]

EXAMPLE An example of an optical waveguide type optical modulator according to the present invention will be described with reference to FIG.

In FIG. 1, parts corresponding to those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

The optical waveguide type optical modulator according to the present invention shown in FIG. 1 is a compound semiconductor quantum well forming the compound semiconductor multiple quantum well layer 3 in the conventional optical waveguide type optical modulator described in FIG. layer 3a is, instead of have a thin 12nm thickness less than L _a than Bohr radius, smaller than the Bohr radius, although thicker than 12nm have a thickness of less than L _a '20 nm, also, The quaternary system of InGaAlAs forming the compound semiconductor quantum well layer 3a forming the compound semiconductor multiple quantum well layer, the wavelength λ _{0 of the} light L to be modulated which is incident on the light incident end face 5a of the optical waveguide 5. From the wavelength λ _{0 in} a direction shorter than the wavelength λ _{0 in} terms of the energy conversion value of the wavelength, the composition has such a composition that a wavelength separated by 25 to 38 meV is obtained as an absorption edge wavelength, and the compound semiconductor quantum well layer 3a is formed. InGaAlAs quaternary system is represented by the chemical formula of In _1-xY Ga _x Al _y As,
As shown in FIG. 2, the compound semiconductor barrier layer 3b having a composition in which y in the chemical formula is a value of 0.11, for example, and the wave function is The compound semiconductor quantum well layer 3a has a thickness of 5 nm or more, which is obtained with almost no overlap between the compound semiconductor barrier layer 3b and the adjacent compound semiconductor quantum well layer 3a.
_Instead of having a thickness L _b equal to or less than that of the compound semiconductor quantum well layer 3a adjacent to the compound semiconductor barrier layer 3b, the wave function is obtained 5
It has the same configuration as that of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, except that it has a thickness L _b ′ of less than nm.

The above is the configuration of the embodiment of the optical waveguide type optical modulator according to the present invention.

The optical waveguide type optical modulator according to the present invention having such a configuration has the same configuration as that of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, except for the matters described above. Therefore, as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, the light L to be modulated is made to enter the optical waveguide 5, and at this time, the first and second electrodes are provided. By applying the modulation voltage V _i between 7 and 8,
Although detailed description is omitted, light whose intensity is modulated according to the value of the modulation voltage V _i is the light to be modulated is the light emitting end surface 5b.
It is possible to obtain the same function as an optical waveguide type optical modulator similar to the case of the conventional optical waveguide type optical modulator described above with reference to FIG.

In the optical waveguide 5, the compound semiconductor quantum well layers 3a and the compound semiconductor barrier layers 3b are alternately laminated in the same manner as in the conventional optical waveguide type optical modulator described above with reference to FIG. Since the compound semiconductor multiple quantum well layer 3 is used, a detailed description thereof will be omitted, but the intensity-modulated light L'is the same as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. As compared with the case where the optical waveguide 5 is made of the compound semiconductor multiple quantum well layer 3 instead of the compound semiconductor layer made of the same compound semiconductor, the modulation can be performed at a higher speed.

Further, the compound semiconductor quantum well layer 3a constituting the compound semiconductor multiple quantum well layer 3 has the same structure as that of the conventional optical waveguide type optical modulator described above with reference to FIG.
Since it is a quaternary system of GaAlAs, a detailed description thereof will be omitted, but the intensity-modulated light L'is converted into the compound semiconductor quantum well layer 3a as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. Instead of the InAlAs ternary system, InG
It can be obtained with high efficiency as compared with the case of using the ternary system of aAs.

The compound semiconductor barrier layer 3b forming the compound semiconductor multiple quantum well layer 3 is made of InAlA, as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG.
Since it is a ternary system of s, a detailed description thereof will be omitted, but even if the light L to be modulated has a high intensity, as in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. Saturation occurs in the operation in which the light L to be modulated is modulated by the modulation voltage V _i , or the light L to be modulated is modulated in the voltage V _i.
There is no reduction in the speed of the operation modulated by.

However, in the case of the optical waveguide type optical modulator according to the present invention shown in FIG. 1, the compound semiconductor quantum well layer 3a constituting the compound semiconductor multiple quantum well layer 3 included in the optical waveguide 5 is thicker than 12 nm. The InGaAlAs layer has a thickness of 20 nm or less and is thicker than that of the conventional optical waveguide type optical modulator described above with reference to FIG. Four
The original system is the light L to be modulated which is incident on the light incident end surface 5a.
The wavelength λ ₀ is shorter than the wavelength λ _{0, and} the wavelength is 25 to 38 meV away from the energy conversion value in terms of the energy conversion value. As is clear from FIGS. 3 and 4,
The absorption of excitons in the compound semiconductor multi-quantum well layer 3 is T even when the light L to be modulated is a TE wave.
Even in the case of M-wave, absorption of excitons composed of heavy holes and heavy electrons and absorption of excitons composed of light holes and light electrons are mixed absorptions at wavelength positions of almost the same absorption. Moreover, the absorption edge wavelength λ _{m of the} compound semiconductor multiple quantum well layer 3 included in the optical waveguide 5 is a modulation voltage applied between the first and second electrodes 7 and 8 and having a negative value on the first electrode 7 side. shifted by V _i, the same shift amount ΔE and described for the conventional optical waveguide type optical modulator shown in the FIG. 7
However, as is apparent from FIG. 5 shown in comparison with FIG. 9, even when the light L to be modulated is a TE wave, T
Even in the case of M-wave, a significantly larger value can be obtained as compared with the case of the conventional optical waveguide type optical modulator described above with reference to FIG. 7, and accordingly, the absorption of the compound semiconductor multiple quantum well layer 3 is accordingly increased. The coefficient has almost the same value regardless of whether the light to be modulated is a TE wave or a TM wave, and compared with the case of the conventional optical waveguide type optical modulator described above with reference to FIG. It can be obtained with a significantly large value.

Therefore, according to the optical waveguide type optical modulator according to the present invention shown in FIG. 1, the intensity-modulated light L'has the same degree of modulation as that of the conventional optical waveguide type optical modulator described in FIG. Thus, the modulation voltage V _i can be obtained at a high speed with a lower value than in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. 7.

The compound semiconductor barrier layer 3b forming the compound semiconductor multiple quantum well layer 3 has a thickness L _b ′ of less than 5 nm, and the thickness L _b ′ is as described above with reference to FIG. Since it is thinner than the case of the conventional optical waveguide type optical modulator described above, the intensity-modulated light L ′ is converted into the modulation voltage V _i as shown in FIG.
In comparison with the above-mentioned conventional optical waveguide type optical modulator, the value is lower and the optical modulator can be obtained at high speed.

From the above, according to the optical waveguide type optical modulator according to the present invention shown in FIG. 1, as is apparent from FIG. 6 shown in comparison with FIG.
Can be obtained at a high speed with a lower value of the modulation voltage V _i than in the case of the conventional optical waveguide type optical modulator described above with reference to FIG. 7.

In the above description, only one embodiment of the optical waveguide type optical modulator according to the present invention is shown, and the n-type may be read as p-type and the p-type may be read as n-type. Besides, various modifications and changes may be made without departing from the spirit of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of an optical waveguide type optical modulator according to the present invention.

FIG. 2 is a diagram for explaining a composition of a compound semiconductor quantum well layer forming a compound semiconductor multiple quantum well layer included in the optical waveguide of the optical waveguide type optical modulator according to the present invention shown in FIG.

[3] compounds constituting the compound semiconductor multiple quantum well layer optical waveguide of the optical waveguide type optical modulator according to the present invention has shown in FIG. 1 semiconductor quantum well layer of 14nm thickness L _a '
FIG. 6 is a diagram showing the absorption coefficient of a compound semiconductor multiple quantum well layer in the case where the compound semiconductor barrier layer has a thickness L _b ′ of 4 nm as viewed by a light absorption current.

4 is a compound semiconductor quantum well layer forming a compound semiconductor multiple quantum well layer included in the optical waveguide of the optical waveguide type optical modulator according to the present invention shown in FIG. 1 having a thickness L _a ′ of 18 nm.
FIG. 6 is a diagram showing the absorption coefficient of a compound semiconductor multiple quantum well layer in the case where the compound semiconductor barrier layer has a thickness L _b ′ of 4 nm as viewed by a light absorption current.

FIG. 5 shows the electric field strength (KV) depending on the modulation voltage applied between the first and second electrodes in the compound semiconductor multiple quantum well layer of the optical waveguide of the optical waveguide type optical modulator according to the present invention shown in FIG. FIG. 4 is a diagram for explaining a shift amount ΔE (meV) of an absorption edge wavelength with respect to / cm) in terms of energy conversion value.

6 is a diagram showing the relationship between the intensity (dBm) of light transmitted through the optical waveguide with respect to the modulation voltage (V) applied between the first and second electrodes of the optical waveguide type optical modulator according to the present invention shown in FIG. FIG.

FIG. 7 is a schematic perspective view showing a conventional optical waveguide type optical modulator.

8 is a compound semiconductor quantum well layer forming a compound semiconductor multiple quantum well layer included in the optical waveguide of the conventional optical waveguide type optical modulator shown in FIG. 7 having a thickness L _{a of} 8 nm; When the barrier layer has a thickness L _{b of} 5 nm,
FIG. 4 is a diagram for explaining an absorption coefficient of a compound semiconductor multiple quantum well layer.

10 is an electric field strength (K) due to a modulation voltage applied between the first and second electrodes of the compound semiconductor multiple quantum well layer of the optical waveguide of the conventional optical waveguide type optical modulator shown in FIG.
FIG. 9 is a diagram for explaining a shift amount ΔE (meV) as an energy conversion value of an absorption edge wavelength with respect to V / cm).

11 is a graph showing the relationship between the intensity (dBm) of light passing through the optical waveguide with respect to the modulation voltage (V) applied between the first and second electrodes of the conventional optical waveguide type optical modulator shown in FIG. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compound semiconductor substrate 2 Compound semiconductor clad layer 3 Compound semiconductor multiple quantum well layer 3a Compound semiconductor quantum well layer 3b Compound semiconductor barrier layer 4 Compound semiconductor clad layer 5 Optical waveguide 5a Light incident end face 5b Light emitting end face 6 Compound semiconductor electrode layer 7, 8 electrodes

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[Procedure amendment]

[Submission date] June 1, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of an optical waveguide type optical modulator according to the present invention.

FIG. 2 is a diagram for explaining a composition of a compound semiconductor quantum well layer forming a compound semiconductor multiple quantum well layer included in the optical waveguide of the optical waveguide type optical modulator according to the present invention shown in FIG.

[3] compounds constituting the compound semiconductor multiple quantum well layer optical waveguide of the optical waveguide type optical modulator according to the present invention has shown in FIG. 1 semiconductor quantum well layer of 14nm thickness L _a '
FIG. 6 is a diagram showing the absorption coefficient of a compound semiconductor multiple quantum well layer in the case where the compound semiconductor barrier layer has a thickness L _b ′ of 4 nm as viewed by a light absorption current.

4 is a compound semiconductor quantum well layer forming a compound semiconductor multiple quantum well layer included in the optical waveguide of the optical waveguide type optical modulator according to the present invention shown in FIG. 1 having a thickness L _a ′ of 18 nm.
FIG. 6 is a diagram showing the absorption coefficient of a compound semiconductor multiple quantum well layer in the case where the compound semiconductor barrier layer has a thickness L _b ′ of 4 nm as viewed by a light absorption current.

FIG. 5 shows the electric field strength (KV) depending on the modulation voltage applied between the first and second electrodes in the compound semiconductor multiple quantum well layer of the optical waveguide of the optical waveguide type optical modulator according to the present invention shown in FIG. FIG. 4 is a diagram for explaining a shift amount ΔE (meV) of an absorption edge wavelength with respect to / cm) in terms of energy conversion value.

6 is a diagram showing the relationship between the intensity (dBm) of light transmitted through the optical waveguide with respect to the modulation voltage (V) applied between the first and second electrodes of the optical waveguide type optical modulator according to the present invention shown in FIG. FIG.

FIG. 7 is a schematic perspective view showing a conventional optical waveguide type optical modulator.

8 is a compound semiconductor quantum well layer forming a compound semiconductor multiple quantum well layer included in the optical waveguide of the conventional optical waveguide type optical modulator shown in FIG. 7 having a thickness L _{a of} 8 nm; When the barrier layer has a thickness L _{b of} 5 nm,
FIG. 4 is a diagram for explaining an absorption coefficient of a compound semiconductor multiple quantum well layer.

9 is a field intensity (KV) due to a modulation voltage applied between the first and second electrodes of the compound semiconductor multiple quantum well layer of the optical waveguide of the conventional optical waveguide type optical modulator shown in FIG.
FIG. 4 is a diagram for explaining a shift amount ΔE (meV) of an absorption edge wavelength with respect to / cm) in terms of energy conversion value.

10 is a graph showing the relationship between the intensity (dBm) of light passing through the optical waveguide with respect to the modulation voltage (V) applied between the first and second electrodes of the conventional optical waveguide type optical modulator shown in FIG. FIG.

[Description of Reference Signs] 1 compound semiconductor substrate 2 compound semiconductor clad layer 3 compound semiconductor multiple quantum well layer 3a compound semiconductor quantum well layer 3b compound semiconductor barrier layer 4 compound semiconductor clad layer 5 optical waveguide 5a light incident end face 5b light emitting end face 6 compound Layers for attaching semiconductor electrodes 7, 8 electrodes

Front Page Continuation (72) Inventor Susumu Kondo 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A compound semiconductor substrate having a first conductivity type, (i) (a) a compound semiconductor clad layer having a first conductivity type, (b) a compound semiconductor quantum well layer, and a compound semiconductor barrier layer. A compound having a structure in which are sequentially and alternately stacked, and neither an impurity giving a first conductivity type nor an impurity giving a second conductivity type opposite to the first conductivity type is intentionally introduced. The semiconductor multiple quantum well layer and (c) the compound semiconductor clad layer having the second conductivity type are laminated in this order, and (ii) the light incident end face on which the light to be modulated is incident, and An optical waveguide having a light emitting end face from which the intensity-modulated light of the light to be modulated is emitted is formed, and a first layer is formed on the optical waveguide via a compound semiconductor electrode attachment layer having a second conductivity type. Electrode of the above compound The opposite to the optical waveguide of the substrate,
The compound semiconductor quantum well layer, which is provided with a second electrode and constitutes the compound semiconductor multiple quantum well layer, is a quaternary system of InGaAlAs and has a thickness smaller than the Bohr radius, The compound semiconductor barrier layer forming the quantum well layer is a InAlAs ternary system, and the wave function is obtained with almost no overlap with the compound semiconductor quantum well layer adjacent to the compound semiconductor barrier layer. In the optical waveguide type optical modulator having a thickness, the compound semiconductor quantum well layer forming the compound semiconductor multiple quantum well layer has a thickness of more than 12 nm but not more than 20 nm. The quaternary system of InGaAlAs forming the compound semiconductor quantum well layer of the layer is
The wavelength separated by 25 to 38 meV in the energy conversion value of the wavelength in the direction shorter than the wavelength of the light to be modulated which is incident on the light incident end surface of the optical waveguide is the absorption edge of the compound semiconductor multiple quantum well layer. An optical waveguide type optical modulator having a composition obtained as a wavelength, wherein the compound semiconductor barrier layer forming the compound semiconductor multiple quantum well layer has a thickness of less than 5 nm.